Rotatable hone



Jan. l5, 1957 H. R. BILLETER ET Ax.

ROTATABLE HONE 3 Sheets-Sheet 1 Filed May 17, 1955 IN V EN TORS.

Hen

Illlllllll l Illll IIIIUUIII IIINIIIIIIIxHHIIlI wif Jan. 15, 1957 H. R. BILLETr-:R ET Ar.

ROTATABLE HONE 3 Sheets-Sheet 2 Filed May 17, 1955 INVENTORS.

Jan. 15, 1957 H. R. BILLETER ET Ax.

ROTATABLE HONE 3 Sheets-Sheet 5 Filed May 17, 1955 QQ SQ w QS United States Patent ROTATABLE HON-E Henry Robert Billeter, Deerfield, and Walter P. Kusllmuk, Chicago, lll., assignors to Ammco Tools, luc., North Chicago, Ill., a corporation of Illinois Application May 17, 1955-, Serialy No. 508,928y

Claims. (Cl. 51-1t8f4.3)

The present invention relates to rotatable cylinder hones and more particularly honessuitable for 'honing' small bore cylinders, such as brake cylinders, piston pinv holes and the like.

The hone of the invention is of the general eharacter that includes a body with a plurality of abrasive' units mounted thereon and adjustably movable 'in directions but permitting their easy removal byapplication of'deliberlate manual force.

Another object is to provide a simple and .ruggedlmeansfor retaining the abrasive units on the body enabling their removal therefrom merely by the simple manipulationl of over-expanding the units.

Another object is to provide novel adjusting means fini a hone of the above general character that is unusually simple, rugged and inexpensive. v

Other objects and vadvantages ofthe invention-willfap-l pear from the following detail description takenin cori-n junction with the accompanying drawings in which:

Figure l is a side elevational view'offa hone vernibody-iirg the invention, showing the labrasive units in partially expanded position;

FigureZ is an enlarged fragmentary elevational -yiewof aportion of the hone of Figure '1, showing thewabraw units ina somewhat expanded position; 'l

Figure 3fis a sectional view, on an Aenlarged scale, daken on line 3 3 of Figure l; v

Figure 4 is a sectional View taken on line 44 =of`Figure 2;

Figure 5 is a longitudinal sectional view lta'lte'rron line 5-5 of Figure 2; Figure 6 is' a sectional view taken online 6-#6 of Fig".v ure 5;

Figure 7 is a sectional View :taken on line 177vof Figure 5;

Figure .8 is a sectional vView taken on line v8"-)8 effig ure 5; f

Figure 9 isa perspective view :of the Iclip interconnecting the abrasive units andthe expandingfiklob;

Figure 10 is an enlarged sectional viewtaken on line 10-10 of Figure l; f

Figure l1 is an elevational view of amodified form lof hone;

Figure 12 is 4a longitudinal sectional view taken-on linen-12 of Figure 111;

2,777,259 Patented Jan. 15, 1957 118" supporting the abrasive units 14, a shank portion 20,

preferably cylindrical and constituting the means by which the hone is mounted in a driving device and, at the end'kopposite the shank 20, a stem 22 on which an expansion knob 24 is adjustably mounted for expanding and contracting the abrasive units. The manner of expand'- in'g the units will be described fully hereinafter. The shank 20 'is mounted in' a suitable manner in a known type of driving means (not shown) for rotating the hone', the abrasive units 14 being rotated with the shaft 16 for performing vthe surfacing operation.

'A known type of centering cone 26 is preferably in# v eluded in the device, being slidably mounted onthe shank 20' lfor the usual purpose, namely, `that when the device is used, for example, in honing a piston pin bore or'bearing, the head 12 is disposedin one portion ofthe bore and the' centering cone held to the opposite and aligned portion, `whereby the hone 'is properly aligned with the axis of they two bore portions. l

The body portion 18, as shown particularlyin Figures 3, tand 10, is polygonal (preferably hexagonal) in cros's section,v and particularly it has oppositely disposed, parallel side bearing surfaces 28 against which certain side portions of the abrasive units 14 are disposed and ,effectively retained for rotation of the abrasive units in response tol rotation of the body portion 18.

The abrasive units 14 referred to above are arranged for expansion and contraction movements on the body portion 18 and these movements are produced by a cam-v nring action. The elements for effecting such action are mounted von the abrasive units and on the body portion 18; Those preferably include a plurality of pins 30 litted inapertures in the body portion 18 and projecting from the ,opposite side bearing surfaces 28 mentioned. The pins 30 may be secured in any desired manner, as by a press fit, and are spaced at suitable intervals, preferably uniformintervals, being of a .sufficient number (e. g. four) tovprovide adequate support for the abrasive units according to the length of the latter, for imparting the desired stability to the unit.

The labrasive units 14, identical in shape, each includes a channel shaped carrier 42 and a plurality of Aabrasive elements or stones 44 mounted thereon. Each channel 42 includes 'a web portion 46 and side anges 54 and 56, withcam surfaces 60 positioned to engage the cam pins 30 respectively. The cam pins 30 .and .surfaces-60 effect expansion of the units in a manner to be described fully hereinafter. The web portion `46 or roofha's transversely angled portions corresponding generally in arrangement with lthe polygonal surfaces of the body :por tion 18. ,The two angularly disposed side' portions 4.8 of the web are so arranged that the .abrasive elements y44 thereon are disposed at approximately 60 apart yas feX- directly on the corresponding surface while the other is` disposed outwardly of the adjacent flange f the other carrier and bears against the latter. shown best in Figure l0. The flange 56 (right hand flange as viewed in Fig. l0) `of the upper carrier bears directly on the side surface 28 at one side of the body portion 18, while the flange on the opposite side of the body portion which bears directlyon the opposite side surface 28 is the corresponding flange 56 of the lower carrier 42. Likewise the flange 54 on that side (left hand side) of the device is disposed outwardly of the flange 56 of the lower carrier. `The flanges on the two carriers overlap at all times. In fully or nearly fully expandedlposition (Fig. 8) theyextend past the central transverse plane, and in collapsed position they overlap or overlie one another substantially completely (in vertical direction, as shown for example in Fig.` 10).

. The inner flange 56 of each carrier which directly engages the corresponding side bearing surface 28 of the body portion 18 is provided with a slot 58 forireceiving a` corresponding detent ball 34, of detent means, fortreleasably` retaining the abrasive units on the body portion. The detent means, forming an important feature of the invention, isiindicated in its entirety at 32 (see Fig. 10) and` preferably takes the form of a pair of such detent balls 34 disposed in a transverse bore 36 in the body portion and opening through the side bearing surfaces 28. The bore36 is parallel with the bores in which the cam pins 30 are mounted. The balls 34 are urged outwardly by` a compression spring 38 confined between the two balls, and retained in the bore by inwardly directed portions 40, formed as by peening, at the ends of the bore. The dimensions of the bore and balls are such, as shown in Fig. l0, that the balls project out of the bore a distance suflicient to enter the slots 58 in the flanges 56 and produce airetaining effect on the abrasive units.

The slots 58 are arranged in positions inclined to the longitudinal axis of the hone, as shown in Figure l, so as to enable constantengagement of thetdetent balls 34 in those slots in response to the movement of the abrasive unit `in expanding and contracting directions. The slots 58 on .Opposite sides of the hone are disposed oppositely, corresponding to the direction of movement of the respective abrasive units.

The arrangement of the flanges 54 and 56 with respect to the body portion 18 results in a staggered relation, i. e., in progressing transversely through the device, as oriented 1n Figure 10, the anges considered serially are alternately opposite with respect to the twoabrasive units, and any tendency to cock or rotate the abrasive units about the axis of rotation is effectively countered by this staggered relation. For example, considering the direction of rota tion as clockwise (Fig. l0) as indicated by the arrow 59, the top unit or carrier would tend to be cocked or rocked counterclockwise relative to the body portion 18. Any such relative cocking or rockingwould tend to spread the flanges of that carrier upon engagement with the corners of the body portion between adjacent surfaces. How- The arrangement `is.

sists the tendency to the spreading action. The same effect is produced on both sides of the hone. The carriers 42 may have a limited degree of resiliency since they are stampings but from a practical standpoint the resiliency is not substantial. The shape of the return bend portions 52 on opposite sides of a channel are of different angular directions because of the staggered relation, i. e., the portion 52 connected with the flange 56 is disposed at a smaller angle to the flange than the opposite portion because the flange 56 is innermost with respect to the proximate flange 54. The arrangement, however, is symmetri cal in this respect around the hone.

The cam surfaces 60 corresponding to and engageable with the respective cam pins on the body are arranged so that the two `cam surfaces on the two flanges of the carriers that engage one end of a cam pin are disposed at opposite angles. The expansion and contraction movements of the abrasive units, as was pointed out above, is produced by longitudinal movement thereof, and this movement acting through the camming elements produces the radial expansion and contraction movements. The resulting movement therefore is in a direction inclined to the axis of the hone. Hence the slots 58 being at the same angle as the corresponding cam surfaces 60 enables the abrasive units to be moved while the detent balls 34 remain in fixed relation longitudinally of the hone. The expansion knob 24 serves to positively expand the abra- A sive units aswell as to positively contract them. The

ever, because the flange 54 on the bottom carrier is dis- 'l posed outwardly of the adjacent flange 56 ofthe upper carrier, the tendency of the flange 56 to spread is checked by the flange 54 in engagement with it and also by the detent. Such spreading action would result in springing out of the lower edge of the flange 56 but this lower edge is adjacent'to the return bend portion 52 of the lower carrier which, in turn, is close to the web portion of that carrier, so that a mechanical advantage relative to the flange 56 is established because the reaction is exerted against the lower edge of the flange 56 which would have the greater swinging movement, and accordingly re-` connection between the expansion knob and the abrasive units takes the form of a detachable clip 62 (shown particularly in Fig. 9) preferably of unitary form, as provided by a stamping formed preferably of spring material, and includes a central U-shaped portion 64 and side leg portions 66 which merge into longitudinally extending arms 68 which, in turn, terminate in outturned ears 70. The clip 62 is positioned in the hone on the body portion 18 between the expansion knob 24 and the abrasive units 14.` For this purpose the body portion has a reduced portion 72 (Fig. 7) on which the side legs 66 resiliently but firmly bear.

'The reduced portion 72 of the body portion extends transversely a sufficient distance that the longitudinally extending arms 68 of the clip 62 are disposed on opposite sides of the body portion 18, and the outturned ears 70 are disposed respectively in the slots 74 in the carriers 42 and in a circular cavity 76 in the expansion knob 24. Each flange in each carrier has a slot 74 which opens through the respective side edge of the flange (Fig. 2), and the slots in the two flanges on each side form a single slot with closed ends into which the outturned ears 70 project. Thek expansion and contraction of the abrasive units results in lengthening or shortening of the close-end slots, and their longitudinal dimension, when shortened, is greater than the transverse dimension of the ears 7 0. The reduced portion 72 of the body` portion is of appropriate length (Fig. 5) for accommodating the clip in the longitudinal movement of the latter in the expanding and contracting movements of the hone.

The insertion of the ears 70 at the opposite end of the clip into the circular cavity 76 in the expansion knob 24 may be accomplished before the expansion knob is threaded onto the stem 22, `by springing of the ends of the arms 68 inwardly toward each other, and thereafter the expansion knob is turned up to a position approximating that of Figure 5, and the carriers 42 are then fitted on'the bodyby their being snapped over the detent balls, the open end of the slots 74 in the carriers receiving the ears 70 and accommodating such movement of the carriers.

armate ears 70 on respectively opposite sides lfor moving the clip in llongitudinal directions. rllhe axial :dimension of :this `cavi-ty is ygreater than that of the ears to provide a limited amount of play therebetween.. A collar .84 Vis rslidingly mounted in bore 86 ofthe expansion knob and urged loutwardly .by a compression spring 88 in the bore linto yieldinglengagement with the end of the clip.

The hone is of pre-set type, the expansion of the abra sive units being accomplished by adjustment of the 'expansion -knob 24. The -knob is rotated 1in a -direction to cause it to advance inwardly (to the right as viewed in Fig. 1.) `for expanding the units, this action forcing the clip 62 .in an .inward direction and hence the 1units `in 'the lsaline direction. This longitudinal or axial movement of the .units effects a corresponding -action `of the camming elements 30 and 60 and produces .radial yexpansion of the units. For a -honing -or surfacing operation, the units are expanded for bringing the abrasive elements into firm engagement with vthe cylinder surface being treated., and as the operation continues, the spring 88 produces continued yieldable expanding pressure 'on :the units.

The expansion knob is turned in the opposite direction -to contract the units. This movement of the knob moves Ithe abrasive units -in that direction longitudinally, and, in yresponse thereto, the detent balls 34, acting in the inclined slots 58 move the abrasive units radially inwardly.

The detent means 32 serves as a Very simple and effective means for retaining the abrasive units on the body portion, .and facilitating placing the units thereon and removing `them therefrom. To place the units 'on the body, the .flanges of the carriers are fitted to the opposite -sides of the body portion yand simply forced over the balls 34, permitting the balls to snap into the slot 58. The open; face character of the cam surfaces -60 facilitates vfitting the units to the body member by such simple movements; The units are removed in as simple a manner, in a reverse movement. The detent means thus serves the dual purpose of releasably retaining the carriers on the body portion and camming the carriers inwardly in contracting direction. I

The hone is of unusually simple and rugged construction throughout, with little likelihood of losing accuracy .l ybetween the various elements thereof.

'-Ifhe second embodiment-of the hone, illustrated in Figs. lll rto 14, is somewhat similar to the hone of the first embodiment but includes a different form of means for contracting the abrasive units. The present hone is of the ty-pe for use in a honing machine (not shown) although 'the principles of this form of the invention `are equally applicable to the se -up type `of hone of the first embodiment.

The hone of Figs. ll lto .14 includes a honing head designated generally at 91, and a tubular drive .shaft 92 adapted for mounting in a honing machine for rotation about its longitudinal axis by suitable operating means in the honing machine. A body 94 is mounted in the (drive shaft for rotation therewith, by suitable means, such .as lby a screw-threaded connection 96 including threads in the inner surface of the drive shaft and on a reduced extension 98 on the body.

The tubular drive shaft 92 includes an actuating rod or plunger 100 mounted for axial sliding movement therein, under suitable control of the honing machine in which the lione is mounted, this operating mechanism being well known. The actuating rod 100 is effective for expanding and contracting the abrasive units 102 in response to the longitudinal sliding movement of the rod, as will be brought out more fully hereinafter.

The body 94 is preferably polygonal in cross section (Fig. 13) and has diametrically opposite bearing surfaces 104 similar Vto the hone yof the previous embodiment. Ex panding cam pins 106 are secured in the body and arranged w-ith their end portions extending through the surfaces 104, as shown best in Fig. 12. In the present instance the honing head 91 -is rather rshort and twosuch expanding -cam pins 106 are .sufficient for producing the expanding movement. A Acontracting c-am pin 108 also mounted in the body and similarly larranged with its yend portions projecting through the opposite :side .bearing surfaces 104, being preferably disposed between the expanding cam pins 106. These pins may 'be vsecured in the body in a suitable manner such as by a press "ft.

The abrasive units .102 are two in number as the {irst embodiment and are 'arranged on opposite sides of the vbody 94. The units 102 are videntical in `construction and shape, and each includes `a channel shaped carrier 109 having a web .1-10 and side flanges 112 'and 114. The web 110 has inclined side portions 116 on which the abrasive elements or stones 118 are mounted, the latter extending a suitable distance longitudinally of vthe carriers in accordance with the .intended dimension of the effective portion yof the .honing head, as shown in Figs. 11 and 12. The units are arranged with their lianges in staggered rel-ation `as in the previous embodiment, the side flanges 11.2 and 11'4 of the two vunits beingin alternate overlying relationship. The flanges 114 of the two units directly engage the respective side bearing surfaces of the body and the flanges 112 engage the outer surfaces of flanges 114 (Fig. 13). Thus, progressing in direction :transversely through the head, as oriented in Fig. 13, all of .the flanges taken in the aggregate areal'ternately arranged; that is, each unit has one flange directly engaging the corresponding bearing surface of the body and its other flange direct-ly engaging the corresponding inner flange of the other unit. The fian'ge 114 is of lesser depth than the fiange112, enabling the units to be contracted a maximum extent (Fig 13) while enabling the outer flange 112 in each case to overlie the proximate flange 114 to a maximum extent.

Each flange 112, 1114 includes three cammi'ng surfaces for engagement respectively with the three cam pins 106, 106 and 108. These cam surfaces are most clearly shown in Fig. 14 which illustrates one of the abrasive units detached `from the hone, in side elevational View, and with the flange 114 presented to the observer. The cam surfaces include two expanding cam surfaces which engage the expanding cam pins 106, and a contracting cam surface 122 which engages the contracting cam pin 108. The expanding cam surfaces 120 and the contracting cam surface 122 are parallel, and spaced apart, as shown, with the contracting surface 122 intermedia-te the two expanding surfaces, l

The flanges 112, 114 are provided with open-ended slots 124 adjacent one end for reception of the outturned ends 126 of the legs 128 of a forklike clip or actuating connector 130. The legs 128 are interconnected yby an end piece 132 having an aperture receiving extension 134 on Athe end of theA rod 100. A compression spring 136 surrounds the reduced extension 134 and is compressed between the end piece 132 andthe inner end of a bore 138 formed in the reduced extension 98 of the body. The body is provided with grooves 140 for receiving the legs of the clip 130, the grooves being of appropriate width for slidingly receiving the latter without undue side play.

The cli-p constitutes the means transmitting to the abrasive units the movement of the rod 100 longitudinally for expanding and retra'cting the units, the clip being moved in expanding direction (to the right, as viewed in Figs. ll and l2) by the rod 100, and in the opposite and contracting direction by the spring 136. Upon 'Inovement of the clip 130 in expanding direction, and consequent movement of the units in that direction, the cam surfaces 120 ride up on the cam pins 106, causing the abrasive units to expand in radial direction. Since ,the cam surfaces 122 have the same slope `as the surfaces 120, the expanding movement is effected without interference by the pin 108. Upon movement of the clip 130 in the opposite direction (to the left as viewed in Fig. ll) the abrasive units are drawn longitudinally in that direction, and the contracting cam surfaces 122,.

acting' on the cam pin 108, move the abrasive units radially inwardly in contracting direction. During movement in each direction the outturned ends 126 have sliding movement in the slots 124 which are of suicient depth to permit the units to contract fully without the ends of the closed slots engaging the ends 126.

It will be appreciated that although only a single cam pin 108 for the contracting function is provided, the abrasive units are readily moved bodily in the contracting movement without rocking about the axis of the pin 108, since any tendency to such rocking action is counteracted by one or the other of the two expanding cam pins 106.

The cam surfaces 120, 122 are open-ended, i. e., the slots forming the surfaces receive the respective pins 106, 108 in response to inward movement of the units. Thus the units may be applied to or removed from the body merely by their being tted to the body in lateral movement. This is done when the hone is in overexpanded condition with the clip 130 projected to a position beyond normal fully expanded position. When the units are on the body, the projection of the clip to such conditions causes the cam surfaces 120 to ride up on the cam pins 106 sufficiently to enable the cam surfaces 122 to ride free of the cam pin 108. The operator then merely lifts the units from the body. To attach the units to the body, a reverse succession of the steps is followed, i. e., the clip is moved to over-expanded position, and the units fitted to the body with the slots 124 receiving the outturned ends 126, and the clip is retracted, whereupon the units are drawn longitudinally with the cam surfaces 122 engaging under the respective ends of the cam pin 108, the latter action contracting the units radially inwardly.

The present construction provides an unusually rigid arrangement for camming the abrasive units in both expanding and contracting directions. There is a minimum of parts or elements susceptible of becoming worn or defective. The retention of the units on the hone body is positive in all normal conditions. The units can be attached and detached by unusually simple manipulations.

We claim:

l. A rotatable hone comprising a body having means for connection with driving means, a plurality of abrasive units mounted on the body together having a plurality of longitudinally extending abrasive elements distributed around the hone and each unit having portions disposed on diamctrically opposite sides of the body, detent means in the body yieldingly biased outwardly in directions perpendicular to the side portions of the units and into openings therein for releasably retaining the units on the body. the units being releasable in response to movement thereof in the planes of the side portions. cam surfaces on said side portions of said abrasive units, and rigid pins extending frorn said body, said body being longitudinally movable with respect to said abrasive units whereby said cam surfaces cooperating with said cam pins and said detent means may positively move said abrasive units radially outwardly and inwardly.

2. A rotatable hone comprising a body having means for connection with driving means, a plurality of abrasive units mounted on the body together having a plurality of longitudinally extending abrasive elements distributed around the hone and each unit having lateral flanges fer releasably retaining the units on the body, spring pressed detent balls urged into openings in the fianges for releasably retaining the units on the body, and means for expanding and contracting the units radially.

3. A rotatable hone comprising a body having means for connection with driving means, a plurality of abrasive units mounted on the body together having a plurality of longitudinally extending abrasive elements distributed around the hone and each having lateral flanges respectively on opposite sides of the body, the flanges of the units overlapping and the flanges being alternately disposed as between units and considered in transverse directions so that only one flange of each `unit is proximate the body, a pair of detent balls in the body spring-pressed outwardy oppositely into holes in the respective ones of said proximate flanges, and means for expanding and contracting the abrasive units radially.

4`. A rotatable hone comprising an elongated body having means for connection with driving means, a pair of elongated abrasive units each including a channel shaped carrier having a web and side flanges and each having an abrasive element on the outer surface of the web, the units being mounted on the body with the flanges of each unit on opposite sides of the body, spring pressed detent means in the body retractably projecting into holes in the flanges for releasably retaining the units on the body, the flanges and body having cam elements operatively interengageable for expanding the units radially in response to longitudinal movement thereof, and means on the body for moving the units longitudinally, said holes being inclined complementally to the cam elements in the respective flanges whereby to enable the longitudinal and radial movement of the units with the detent means remaining stationary.

5. A rotatable hone comprising a body, a plurality of axially spaced cam pins in the body projecting from diametrically opposite sides thereof, a pair of abrasive units mounted on the body each including a channel shaped carrier having side flanges disposed on opposite sides of the body and the anges having cam surfaces respectively engaging the pins and operative therewith for expanding the units radially in response to axial movement thereof, means mounted on the body for so moving the units axially, and spring pressed detent balls in the body biased into slots in the flanges for releasably retaining the units on the body, the slots being inclined complementally to the cam surfaces in the respective flanges whereby to enable the axial and radial movement of the units with the detent balls remaining translationally stationary.

6. A rotatable hone comprising a body, a plurality of abrasive units detachably mounted on the body for movement longitudinally, said body having a threaded extension on one end, an expansion knob threadedly mounted on the extension, and a U-shape clip detachably mounted on the body effectively between the units and expansion knob and having axially extending arms on opposite sides of the body with outturned ears on the extremities of the arms, the units having transverse slots receiving the ears on the clip at the respectively adjacent ends, and the expansion knob having a circular cavity receiving the ears at the other end, the cavity having axially and oppositely directed faces for engaging the ears in both directions of axial movement.

7. A rotatable hone comprising a body, a plurality of abrasive units detachably mounted on the body for movement longitudinally and radially, cam means be tween the body and abrasive units for radially expanding and contracting the units in response to movement thereof longitudinally, the units including channels each with flanges on opposite sides of the body arranged with the flanges on the several units overlapping, said body having a threaded extension on one end, an expansion knob threadedly mounted on the extension, and a U-shaped clip detachably mounted on the body effectively between the units and expansion knob and having axially extendv ing arms on opposite sides of the body with outturned ears on the extremities of the arms, each flange having a slot opening through the edge of the flange and arranged so that in the overlapping flanges a closed-end slot is formed in two flanges, the slots being disposed transversely and positioned at the end adjacent the clip, said slots receiving the ears on the clip at the respectively adjacent ends, and the expansion knob having a circular cavity receiving the ears at the other end of the clip, the cavity having axially and oppositely directed faces for engaging the ears in both directions of axial movement and spaced apart to provide for limited play between the knob and clip, and spring means in the knob biasing the clip and thereby the units axially in expanding direction.

8. A rotatable hone comprising a body, a plurality of abrasive units detachably mounted on the body for axial and radial movement, irst cam means on the body, cam means on the units engageable with the said first cam means and eifective for expanding the units in radial direction in response to movement in one longitudinal direction, second cam means on the body, cam means on the units engageable with the said second cam means and eiective for contracting the units in radial direction in response to movement in the opposite longitudinal direction, said cam means being open-ended enabling separation of the units from the body by radial outward movement, and actuating means on the body engaging the units for moving them in longitudinal directions.

9. The invention as set forth in claim 8 in which the first and second cam means on the body consist of pins having end portions projecting out opposite side surfaces of the body, and the cam means on the units consist of inclined surfaces in side portions of the units proximate the said side surfaces of the body.

10. A rotatable hone comprising a body, a tubular drive shaft mounting the body and constituting means for mounting the hone for rotation, said body having diametrically opposite side bearing surfaces, a rst and a second cam pin mounted in the body with end portions projecting outwardly from said side surfaces, a pair of abrasive units detachably mounted on the body each including side ilanges overlying said side surfaces of the body, said side flanges each having parallel but oppositely facing cam surfaces respectively engaging said irst and second cam pins and operative for expanding and contracting the units in radial directions in response to movement in longitudinal directions respectively, an actuating rod slidably mounted in the tubular shaft, and clip means interconnecting the rod and the units for moving the latter longitudinally.

References Cited in the file of this patent UNITED STATES PATENTS 1,002,612 Walther Sept. 5, 1911 1,904,336 Sunnen Apr. 18, 1933 2,419,660 Satterthwaite Apr. 29, 1947 2,663,124 Smole Dec. 22, 1953 

